I used Beagle/fastIBD with default parameters and with the HapMap recombination map to figure out the mean IBD sharing between Dan's chr10 and a number of different populations, including most of my available South Asian references. I also included YRI as an appropriate outgroup, as well as CEU30 and the 1000 Genomes British populations, given that Dr. MacArthur is Australian and has a Scottish surname, so it's a good bet that he has plenty of British-type ancestry.
The mean chr10 sharing is plotted below:
Now, it's cool that the top-2 matches are Argyll and Orkney, both of which are part of Scotland. But, what is interesting, is that North_Kannadi squeezes in ahead of CEU, with a very respectable mean of 1.4cM, and a number of other Indian populations are not far behind, while most of the ones from Pakistan are not. I'd say this looks consistent with an "Indian" origin of this type of ancestry.
A useful control is to repeat this experiment with a different chromosome, the similar-sized chr9 which lacks evidence for South Asian ancestry:
It is now visually clear that the difference between the British populations and the South Asian ones is greatly diminished. And, while the North Kannadi were near the top of the order for chr10, they are near the bottom for chr9, even lower than the YRI outgroup at the "noise left end" of the spectrum. Even the highest ranked South Asian population has about 1/3 estimated IBD sharing as the British ones.
Moreover, whereas in chr10 the top-ranked South Asian populations were often from the south, in chr9 the situation is reversed, with most of the top-ranked ones being from Pakistan. Again, this suggests that there is no real South Asian admixture here, but just some low-level sharing with the (more West Eurasian) populations of the northern part of South Asia.
So, to make a long story short, it does look to me like an excellent suggestion that there is some type of peninsular or even south Indian ancestry in the chr10 in question.